Electromagnetic gearing.



No. 758,293. PATBNTBD APR. 26, 1904. E. M. BENTLEY. ELBGTROMAGNETIG GEARING.

APPLICATION FILED DEO. 2, 1903.

N0 MODEL.

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UNrrnD i STATES Patented .April 26, 1904.

ELEGTROMAGNETIC GEARING.

SPECIFICATION forming part of Letters Patent No. 758,293, dated April 26, 1904.

Application filed December 2, 1903. Serial No. 183,497. (No model.)

' fcation as an illustration of the inventionthat form thereof which I-now regard as the best one of the various forms in which the principle .of the invention may be embodied.

In the drawings, Figures l and 2 show diagrams of circuits; and Fig. 3 shows a machine, partly'in section.

My invention relates to a dynamo-electric machine particularly designed to serve as a transmitting agency between driven and driving mechanism and when so used enables the driving mechanism to operate at a substantially constant or other desired speed, while the drivenl mechanism runs at a speed that varies with respect to that of the driver.

My invention may also be employed in any situation where it is desired to'derive from a dynamo-electric machine the effect of a speed different from that,at which it may actually be running.

Referring to Fig. 1, A represents the winding of a field-magnet, having a commutator A. The winding is like that of an armature, and it is well understood that if current isdelivered to such a winding by brushes bearing on'the commutator at opposite points poles will be produced in the field-magnet at points corresponding in position to the location of the Abrushes on the commutator andk also that the poles may be caused to rotate -by rotating the brushes on the commutator, so as to give the effect of the Well-known rotary poles produced by multiphase alternating currents. In the present case I have shown for convenience a bipolar machine with two hield-magnet brushes aa bearing on commutator A one hundred and eighty degrees apart. In the same figure, B represents an armature-winding connected to a commutator B', with brushes Z bearing thereon in quadrature with brushes a. The machine is connected as a series machine short circuited on itself, the

brushes b being connected to brushes a, so as to put the field and armature in series; In such an arrangement it is manifest that if the ield-magnet and all four brushes be stationary while the armature is rotated the conditions will be those of an ordinary series dynamo and a current will begenerated in the armature which will energize the field-magnet in the usual way. On the contrary, if the armature and allfour brushesl be stationary and the field-magnet rotated no current will be generated, because there will be no movement of the armature-coils with respect to the magnetic lines of force, since the fieldmagnet so predominates in strength as a magnet that if any current could be imagined as flowing it would establish field-magnet poles at the brushes a a, which are stationary with respect to the armature, and not at the brushes b.

This would be the condition of substantially no current. In other words,the field-magnet poles under every condition that will produce current must be at the brushes a a and if those brushes are moved will follow them. From this it appears that if the armature be rotating with respect to the held-magnet we may by rotating the four brushes change the eective or generative movement as distinguished from the total movement to any extent desired. Thus if the field-magnet be stationary and the armature rotates at eight hundred turns per minute whilev the four brushes are rotated in the same direction 'seven hundred and sixty turns per minute the effective or generative movement of the armaturecoils with respect to the field-magnet poles will be but forty turns per minute. Since the brushes may be freely rotated, this effective component can be varied at will, according to the speed of rotation of the brushes. By putting the field-magnet in series with the armature or by otherwise making the potential diiierence between the field-magnet terminals very low the commutating diilculties at the Ieldmagnet commutator will be greatly reduced.

If the described arrangement be utilized in a motor on a constant-potential circuit, a rotation of the brushes in the same direction as the motor rotation will decrease the counter electromotive force of the motor and allow an IOO ' Lwill consist largely in the current factor,

'while` on the other hand, the rotating of the brushes in the opposite direction will increase the counter electromotive force and decrease the current and the motor energy will consist largely in the counter-electromotive-force factor. The rotation of the brushes does not,

.of course, represent energy, but merely produces a self-inductive effect similar to that of a transformer or inductance coil, the induced.

electromotive force being commutated and acting with or against the impressed electromotive force, according to the directionof rotation of the brushes.

The foregoing arrangement may be utilized in various ways, and the rotation of the brushes may be produced by a special motoror by other means and electrical communication with the brushes established by slip-rings in a manner familiar to the art. I have, however, conceived of applying the contrivance to transmit power between a driving-motor-such, for instance, as a gas-engine or a synchronous alternatingcurrent motor which runs at a constant speed or at a speed different from that of the mechanism driven thereby-*and such driven mechanism. To this end I connect one of the members of the dynamo-electric machine, either the field-magnet or armature, to the driving agency and the other member to the driven mechanism and short-circuit them one on the other. In such a situation the machine serves only as a gearing to connect the driver with its load and not as aproducer of power. Hence the slip between armature and field will be only that required to produce enough current to give in the field-magnet such amagnetic field that the resistance which it presents to the traverse of the armature-conductors through it t ill be equal to or greater than the torque required to operate the load. Such acurrent only requires an electromotive force adequate to overcome the internal resistance oi' the machine. If the machine with a given iieldmag net strength would when acting as a generator produce its full load at eight hundred turns per minute, of which load the internal resistance oi' the machine represented five per cent., then but forty turns per minute would be required for giving the same field magnet strength if the external load were removed and the machine short-circuited. Assuming such field-magnet strength to be adequate to resist the driving torque applied by the operating-engine to its load when the machine is interposed between them, then the load would rotate at seven hundred and sixty turns per minute if the engine ran at eight hundred turns. The loss in transmission would be the C2 R loss in the dynamo. These figures would be modified for a series machine, but may be used to illustrate the principle. When, how- 'rasees -of the driven load and correspondingly large slips that I seek to avoid, and I do this by 'constructing the dynamo in the manner illustrated in the diagram of Fig. 1, and then by rotating the brushes I may cause any desired fraction of the total slip to be alone e'ective in producing current. I thus restrict the current-generating capacity of the machine at all times to the point which will enable it to serve its function as a gear without producing needless current as a generator. If `the load runs at haltspeed with a slip of four hundred, the brushes will be rotated three hundredl and sixty and the armature can only traverse the magnetic field at the required rate of forty. This speed of the brushes may be increased or decreased at will to give any torque that will produce the required speedv of the load. At full speed of the load the brushes will stand still, and when the load stands still the brushes will runnearly at the same rateas the slip. This rotation ofthe brushes may bc produced by a motor of any kind and in any desired manner; but for convenience I prefer to rotate them bythe mechanism` itself and to give them a fixed ratio of speed to the slip, so that at all times the effective slip will be a definite number of turns per minute, and then to vary the torque at that slip by means oi' an adjustable resistance either in series withl the ield-magnet and armature or in shunt thereto. Inl Figs. 1 and 3 such a resistance is shown in the latter relation at R; but if it is to be in series it will beinterposed between one of the brushes a and a brush b, as shown in Fig. 2, the necessary slip-rings being provided therefor in an actual machine.

In Fig. 3, B is an armature, and A is a fieldmagnet rotating in bearing d external to the armature-bearin gs e. The armature is driven by any suitablemeans, which is indicated by acrank it', while the field-magnet serves to drive any desired mechanism through a sprocket wheel L. A is the field-magnet commutator and B' that of the armature. One of the brushes of the 'field-magnet is carried by a ring F, which also carries one of the armature-brushes and electrically connects the two brushes. The ring F is free to rotate on a bearing E, insulated from but mounted on the armature-shaft S. ""Ihe remaining two brushes are similarly carried by -ring F', rotating on bearing E. rIhere is thus established a short-circuiting connection from one brush a to ring F, to one brush b,

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slip.

through field-magnet winding to first brush a. Both sets of' brushes are rotated together, the

Vrings F and F' being mechanically connected by an insulating-ringf by means of pinions and G on a common shaft, which has a bearing in the'ring F'. The pinion 1r engages with gear-wheel H on the armature-shaft S, and the pinion G engages with internal gearwheel 'l on the field-magnet frame. This gives the brushes a 'differential rate of' rotation dependent on the gearing ratio in the two sets of gears, respectively. 1f thefield is stationary and the slip eight hundred, then the brushes will rotate seven hundred and sixty in the same direction as the armature. If, however, the field-magnet rotates in the same direction at a speed of' seven hundred and sixty and the slip becomes forty, then the brushes will stand still, the gearing ratio being adjusted to that end. In any event there will be forty turns of the slip available for generation, or, in other words, the rate at which the armature-conductors traverse the magnetic field will be always forty whatever the The shunting resistance Ris connected between two contact-rings on the extremity of' shaft S, which are connected, respectively, to carrier-rings F and F' by means of conduct'crs pressing through the shaft from each contact-ring to one of the bearings E and E', on which the carrier-rings rotate. The connections will then be as diagramed in Fig. 1. It' the resistance R is entirely short-circuited, no current will be generated, and if, n the other hand, it is entirely open-circuited the generated current will be that dueto the relative movement of field-magnet and armature at a rate equal to the rate of speed of' the brushes and with full field-magnet strength. Between these extremes the current will be due to the same speed, but of a value dependent on the field-magnet strength as determined by the adjusting effect of' the shunting resistance R. `Instead of the shunting relation of' the resistance shown in Fig. 1 the series relation shown in Fig. 2 may be provided in a manner obvious to one skilled in the artas, for example, by a slip-ring connection between brush a and brush I), containing the resistance R.

The described arrangement for giving vthe brushes a speed that varies in a definite relation to the slip does not give the utmost economy of which the device is capable, but is one that is convenient and of' an efiiciency that is adequate for most purposes. In the case assumed it would be somewhat more eflicient to give the field-magnet its undiminished strength and then vary the effective slip above or below forty as might be required. For instance, if avery small torque were required it might be secured with an effective slip of'I twenty, and, on the pthervhand, a very large torque might require sixty, vwhile to set it rigidly at forty limits the torque to that afforded by the current which will result from' that slip, and for smaller torques a vslight loss'will be incurred by unnecessary speed of slip. These objections are more than counterbalanced by the simplicity of the arrangement. 1 intend, however, to embrace by this patent all arrangements wherein the actual slip is made effective slip to any desired degree. whether that degree be large or small or whether lit is adjusted exactly or only approximately to the torque or to any other feature thatserves as the object toward which adjustment is directed.

What 1 claim as new, and desire to secure by Letters Patent` is- 1. 'The combination with a dynamo-electric machine having one member movablewith respect to a magnetic field in the other member, of means for adjusting the effective rate of' Such relative movement comprisinga pole* shiftingl device for rotating the poles of' the magnetic field simultaneouslywith the mechanical rotation.

2. The combination with a dynamo-electric machine of a regulator acting to vary the effective rate of relative movement of' field-mag net poles and armature comprising a poleshifter for the field-magnet giving the poles a rotation adjustable for regulation and supplementary to the relative mechanical movement of fieldfmagnet and armature.

3. A regulator for a dynamo-electric machine acting to vary the effective rate of' rela tive movement'of field-magnet poles and armature comprising a pole-shifter for the fieldmagnet giving the poles a rotation adjustable for regulation and supplementary to the relative mechanical movement of field-magnet and armature.

4. A regulator for a dynamo-electric machine acting' to Vary the effective rate of relative movement of' field-magnet poles and armature comprising a continuously-running pole-shifter for the field-magnet operating at a rate adjustable for regulation and different lfrom the rate of relative movement between field-magnet and armature.

' 5. A regulator for a dynamo-electric ma- IOO nov

chine acting to vary the effective rate of relative movement of field-magnet poles and armature comprising a pole-shifter for the fieldmagnet and a motive device therefor givingit a rate adjustable for regulation and different from the rate of relative movement of fieldmagnet and armature.

6. The combination with adynamo-electric machine having one member connected to driven and the other to driving mechanism of means for rendering a portion only of the slip effective for generation off'- current.

'7. The combination with a dynamo-electric machine having one member connected to driven and the other to driving mechanism of means for rotating the magnetic field to produce an eiective slip diierent from the-actual slip.

8. The combination with a dynamo-electric machine having one member connected to driven and the other to driving mechanism of means for closing the armature circuit on itself and means for giving the poles of the held-magnet a rotation supplementary to their mechanical rotation.

9. The combination with a dynamo-electric machine having one member connected to driven and the other to driving mechanism., a commutator for the field magnet, brushes thereon and means for rotating the brushes to give the field-magnet poles a rotation supplementary to the mechanical rotation.

10. The combination with a dynamo-electric machine having both of its members rotatable,

of means for rotating the field-magnet poles within the body of the eldemagnet at a rate diferent from the rate of relative movement of the two members.

11. The combination with a dynamo-electric machine having both members rotatable, of driving mechanism connected to one member and driven mechanism connected to the other member, means for rendering a portion only of the slip effective for generation of current' and a Vref g'ulating device for adjusting the amount of current produced.

l2. The combination with a dynamo-e1ectric machine, of means for renderinga portion only of the relative movement of the two members eiective for generation of current, and a regulator for adjusting the amount of current pro-- duced. I

13. The combination with adynamo-electric machine, of means for rendering a portion only oi' the relative movement of field-magnet and armature eiective for current generation,

electrical connections for putting the Held magnet in series with the armature and an l justableresistance for regulating the current produced. i

14. The combination with adynamo-eleete machine having both of lits members ro of a commutawr for the field-magnet, a com mutator for the armature, a driving emanuela-` tion between the brushes of both eo'mmutltm'l 1 and the shaft of the machine, and a resistance for regulating the generated current.

15. The combination with adynamo-electe machine having both of its members ro of a commutator for both membermcomlmtator-brushes thereon, and dierentielgellef` ing for rotating the brushes bythe dilel'eltv` tial movementof therespective members, slip l ring connections for the rotating brushes a regulating resistanceconnected in circuit` through said slip-rings.

16. The combination with a dynamo-electric machine of a commutator for both field net and armature, rotatingbruehee forv commutatore and a driving connection tween the brushes and the shaft of `the une chine.

17. The combination with drivi1ig 1u\d` driven mechanism, of a dynamo-electric ula-` chine having one member connected tothe former and'the other to the latter mechanism, a`

short-circuiting connection `for thedynamo, ai commutator for bbth heid-magnet and ture, rotating brushes forv both commutatore` and a driving connection between-the rotating; brushes and the shaft of the machine.

In witness whereof I have hereunto set my` hand, before two subscribing witnesses, this` 20th dayof November,y 1903.

EDWARD M. BENTLEY.

Witnesses:

L. T. SHAW, J. B. GATELY. 

